This invention relates to a method for mapping higher brain function to measure higher brain function with accuracy and to a headgear used in the method.
Recently a method for measuring brain activity in a noninvasive manner and for analyzing brain function has been conceived and various devices or systems for the method have been developed. For example, fMRI (functional magnetic resonance imaging) and NIRS (near-infrared spectroscopy) are representative examples of a method for mapping brain function. See, for example, Raichle, Marcus E., “A Brief History of Human Functional Brain Mapping” Brain Mapping, The Systems, Academic Press, 2000, p. 64–65.
The fMRI is primarily based on a BOLD effect that measures a change of signal intensity of MRI based on a fluctuation of deoxygenated hemoglobin (Deoxy-Hb) value of blood in a brain and images it so as to monitor a local brain activity. The fMRI specifies an activated portion from a brain functional image obtained with an extremely high space resolution such as a mm order. In the meantime, the NIRS is to irradiate near-infrared pulse light of a predetermined wavelength on a head portion of a subject through a probe for irradiation (optical fiber) and to detect the corresponding near-infrared light diffused from the brain with a high time resolution such as several tens of milliseconds through a probe for detection (optical fiber). More specifically, oxygenated hemoglobin concentration, deoxygenated hemoglobin concentration and a total hemoglobin concentration of blood in a brain are measured by transmitting near-infrared light through a probe connected to a holder mounted on the head portion of the subject by making use of the near-infrared light having a wavelength that penetrates a skin tissue or a bone tissue and that is absorbed by oxygenated hemoglobin or deoxygenated hemoglobin of the blood, and a brain activity of the subject while exercising or in a stationary state is measured or imaged with a high time resolution by means of a blood circulation kinetics change in the brain of the subject derived from a diachronic concentration change. See, for example. Japanese Patent Specification 2002-128107.
The fMRI is superior in a space resolution as mentioned above, but inferior in a time resolution since, at most only a piece of an image can be imaged in a few seconds. In addition, in order to conduct the fMRI a subject is encased in an almost blocked system and a brain activity of the subject is measured in the system, which makes it difficult to measure the brain activity of the subject, for example, during an exercise with moving his or her body. Further, nowadays the BOLD effect itself is the fundamental principle of the fMRI under review. On the other hand, the NIRS is, as mentioned above, superior in a time resolution and the subject can be monitored in either an unconstrained condition or a constrained condition, however, the monitoring depends on a position where a probe is mounted, thereby performing a low space resolution of a few cm order at most.
Based on the above-mentioned problem, it might be assumed mistakenly that merely combining the fMRI and the NIRS, in other words, just checking both results of the fMRI and the NIRS, covers each weak point and a result of measuring brain function is superior both in the time resolution and the space resolution. However, since it is unclear that results of the fMRI and the NIRS always correspond with each other, merely combining both of the fMRI and the NIRS does not produce an agreeable result.
In order to solve the above problems the present claimed invention mainly intends to provide a method for mapping higher brain function wherein advantages of the fMRI and the NIRS can be demonstrated and the results of both methods can be compliant with each other definitely and to provide a suitable headgear used for the method.